Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/1057

Rh representing the "Saussurite." The external portions of this latter contain much carbonate; but the central mass, or core, consists of a bluish-white compact silicate, or mixture of silicates which, omitting small quantities, has the following composition:—

The compound has more affinity, as regards its percentage of silica, with anorthite than with labradorite; but the presence of so much magnesia and its poverty in alkali must lead us to regard it as a mixture rather than as a mineral species worthy to be classed with the felspars.

The diallage associated with the above is a well-defined mineral, and but slightly affected by ignition or acids. Subjoined is a rough analysis:—

No alkali was found in the specimen examined. The amounts of lime and magnesia, being so exactly equal, indicate a mineral which, in its chemical aspect, is almost equally allied to the augites and the hornblendes.